Berry is a girl living in the data-managed city of Tom Sawyer Island. Her hobby at the moment is trying to catch Phantom Zero, who's believed to be behind the cases of Love loss known as the Zero Phenomenon. One day, when she heads into town to get the broken Deco in one of her eyes fixed, Berry runs into a kid who seems like a ghost, due to being unable to be seen with Deco. Suspecting she may have finally found the Phantom, Berry begins her chase.

Hack is being held at the customer center under suspicion of being Phantom Zero, where she's questioned about the crime of forcibly erasing Love. Meanwhile, Berry learns from the mysterious Finn about how he and his comrades are ghosts, citizens who live in the city despite not being registered. Finn is skeptical that a fellow ghost would have helped Berry, and obtains the data on Phantom Zero from the paper plane device of Hack's that Berry brought.

The Ghost Detective Club has a new case. The client is a professor that uses Deco overlays to create artificial animal that he has on display at his Neo Animal Museum. His self-proclaimed masterpiece, the Nue, has an appearance that doesn't match the listing on Decopeedia, and hires the detective club hoping to clear up the confusion. After getting a glimpse at the professor's Nue, it looks nothing like the cute creature whose picture is on the Decopedia page. Even so, the professor insists that his Nue is the accurate version.

Berry is helping Hank sort through the junk that he has salvaged at the harbor when they encounter an old friend of Hank's, named Will, who informs them about an older model of satellite that's expected to crash down into the nearby sea. Back at the agency, the peacock feather-like circuit that Watson received from Analytica is being analyzed. When Hank returns, he insists that they all head to the area Will tipped them off about.

Thanks to Doron and his drone friends, Berry, Hack, and Finn are able to reach Mark Twain, a strange facility floating in the sky. By using the Angelfish club card they had previously obtained, they manage to get inside, where Berry and Hack enter Mark Twain's rendition of the Hyperverse. What they discover appears to be a labyrinth. Knowing that all the secrets of Tom Sawyer island must be contained within, Berry and Hack start searching for Phantom Zero's identity.